Knee osteoarthritis: what physiotherapy can and cannot do

Two things are usually said to people with knee osteoarthritis, and both are wrong. The first is that nothing can be done until a replacement. The second is that exercise will wear the joint out faster.

What the treatment can honestly claim

Physiotherapy does not regrow cartilage. No injection, supplement or exercise programme does. Anyone promising that is selling something.

What strengthening does do, consistently and across a large body of evidence, is reduce pain and improve what you can do with the knee. For many people that is the difference between stairs being a problem and stairs being fine, and it is the one intervention that delays or avoids a replacement rather than simply waiting for one.

Loading the knee does not destroy it

Cartilage responds to load the way bone and muscle do. Knees that are used within tolerance do better than knees that are protected. The pain you feel walking is not the sound of the joint wearing through.

The practical rule is that discomfort during and shortly after activity which settles within a day is acceptable. Pain that builds over days, or that leaves the knee swollen each time, means the dose was too high — not that the activity was wrong.

What a programme actually involves

Quadriceps and hip strength, which is the single most effective component and the one most often skipped because it is slow and dull.

Range of motion, particularly full extension, which people lose early and miss late.

Weight through the leg, progressed deliberately — sit-to-stand before steps, steps before hills.

Pain relief as a means, not an end. Heat, manual therapy and electrotherapy earn their place by making the strengthening possible.

Where the X-ray fits

Badly, is the honest answer. The correlation between what a knee looks like on film and what it feels like to live in is weak. Knees that look severe on X-ray often function well, and knees that look mild can be miserable. The scan is for ruling things out and for surgical planning; it is a poor guide to what you should do next.

Injections, supplements and the rest

Steroid injections reduce pain for weeks to a few months. They are useful for getting a flare under control so that strengthening can start, and they are not a course of treatment in themselves.

Hyaluronic acid injections have mixed evidence and help some people modestly. Platelet-rich plasma is still being argued about and is often priced as though it were not.

Glucosamine and chondroitin have been studied extensively and perform close to placebo. If a supplement helps you, there is no harm in continuing it; there is no case for relying on it.

Weight, where it is relevant. Each kilogram off reduces the load through the knee several times over at every step, and it is one of the few things with an effect size comparable to strengthening. It is also the advice most often given badly, as an instruction rather than as something to be supported through.

Knee braces and walking aids are worth trying when they let you walk further and do more. Anything that increases your activity is working in your favour.

When surgery is the right answer

When pain wakes you at night regularly, when walking distance has shrunk to the point of changing your life, and when a genuine course of strengthening has been done and has not moved it. A replacement done after that work goes better: you go into it stronger and you come out of it faster.

How long

Six to twelve weeks before strength work changes the day-to-day picture, and it holds only while the work continues. This is a condition that is managed rather than cured, and the management is mostly yours between appointments.